Fragility-based seismic evaluation and GFRP retrofitting of short-span bridge piers in Thailand’s seismic zones

Information from the abstract

The seismic resilience of short-span reinforced concrete (RC) bridges in Thailand remains insufficiently addressed, despite increasing evidence of active faults capable of generating magnitude 6–7 earthquakes. This study proposes an integrated experimental–numerical–probabilistic framework for fragility-based seismic evaluation and glass fiber–reinforced polymer (GFRP) retrofitting of short-span pile-bent bridge piers representative of the Department of Highways (DOH) inventory. A representative 1:2 scale pile-bent pier was tested under quasi-static cyclic lateral loading in accordance with FEMA-461, and two GFRP strengthening schemes were examined for both post-damage retrofitting and pre-strengthening conditions, with results calibrated using nonlinear finite element modeling in ATENA. Experimental and numerical results show that GFRP retrofitting increased peak lateral load capacity by approximately 22–24% for repaired piers, while specimens strengthened prior to loading achieved peak capacities of up to 145 kN and ductility values as high as 6.78. The validated finite element model was subsequently extended to conduct nonlinear pushover analyses, and fragility curves were developed for 24 representative pier configurations across three seismic hazard zones corresponding to 475- and 2,500-year return periods, incorporating material uncertainty through a Monte Carlo-based stratified sampling scheme. Fragility results indicate that unretrofitted piers in high-hazard zones can exhibit collapse probabilities of up to 40%, whereas GFRP retrofitting effectively eliminates collapse under the considered seismic demands. Overall, the proposed framework demonstrates the technical effectiveness and practical applicability of locally manufactured GFRP as a sustainable retrofit solution for enhancing the seismic resilience of Thailand’s bridge network, providing a quantitative basis for regional risk prioritization and retrofit decision-making.

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Related topics: Seismic Performance and Analysis · Earthquake and Tsunami Effects · Coastal and Marine Dynamics